In distribution of movie content in recent years, the number of streams multiplexed to form one digital stream is on the increase. In view of this, the stream selection function mentioned above is regarded as particularly important. Regarding audio, the increase in the number of streams is due to an effort to provide the user with not only main sound of a program but also various kinds of sound such as commentary and BGM.
These audio streams have a specific numbering system. Accordingly, by setting a stream number of one of the audio streams in a status register in a playback apparatus so that the playback apparatus selects the audio stream identified by the stream number in the status register, a particular type of audio stream can be played back at each playback session.
The status register used here is initialized upon factory shipment, and can be updated later by the user. When a plurality of audio streams are multiplexed to form one digital stream, the author may want the user to view a moving picture in combination with a specific audio stream. However, since the setting of the status register is unchanged unless the user updates it, the moving picture may end up being played with a different audio stream contrary to the author's expectation. To avoid this, it may be suggested to store, on a BD-ROM, information for automatically selecting a desired audio stream. However, playback apparatuses widely range from high-function apparatuses capable of decoding audio streams of all kinds of codec to low-function apparatuses capable of decoding only audio streams of a limited kind of codec. If the BD-ROM instructs a playback apparatus incapable of decoding the desired audio stream to select that audio stream, a program occurs.